Evening has fallen in Wantagh, Long Island, and the Jones Beach amphitheatre is filling up with people who have turned out early for a Muse concert. But perhaps the draw is also the opening band.

With their ethereal electronic pop-rock alongside a vociferous support of LGBTQ rights, PVRIS have spent the past three years quietly making their mark. Their 2014 debut album White Noise, carried by piercing vocals from Lyndsey Gunnulfsen (AKA Lynn Gunn), catapulted them to the forefront of alt-rock; US TV performances followed, and they appeared on the Vans Warped tour – a rite of passage for young angsty bands – for four years in a row from 2013. Their second album, this year’s All We Know of Heaven, All We Need of Hell has an even moodier ambience: there are touches of Halsey and London Grammar amid a sleek yet sparse guitar sound.

An hour before they are due on, the three friends from Massachusetts – Gunn, guitarist Alex Babinski and bassist Brian MacDonald – are hanging out in the catering area, ribbing each other. PVRIS were formed while the three were still in their respective high schools, and the wide-eyed enthusiasm of teenagers seems intact. They have had the trajectory many bands dream of: instant recognition from the scene they grew up in, acclaim in the press, and interest from the mainstream.

There’s a lot of camaraderie in our fanbase which creates a safe and accepting space

Lynn Gunn

But they – Gunn in particular – are proof that external circumstances do nothing to solve internal problems. She has spoken frankly in previous interviews of crippling performance anxiety, and as I sit in a coffee shop the day after the gig with the slight, unassuming 23-year-old, I ask her whether that has improved.

“It’s actually gotten worse,” she says. “I’ve always been very generally anxious and nervous before playing but now … I don’t know if it’s because the stakes are higher or if it’s built over time. I’ve been trying to navigate it and rewire things. I try and calm down and meditate before we go on stage.”

By her own admission, the gruelling years of touring following White Noise’s release meant personal issues had to be put to one side. “You have your game face on and you just get on with whatever you’re doing [on tour],” she says. “You can’t face it head-on most of the time because you have to go and do a photoshoot, you have to perform on stage, and you can’t be in that headspace.” When they finally finished that run and had some downtime, Gunn says those suppressed emotions came to the surface, and became the foundations from which the new album grew. The lyrics on the second record feature direct admissions that all was not well: “Don’t need a metaphor for you to know I’m miserable,” Gunn sings on its second single, What’s Wrong.

Gunn’s frankness about her anxiety shows that those living their dreams can have mental health as fragile as the rest of us, and has made her a focus for people looking for comfort in music. “I don’t know if it’s what we’re putting out and attracting back, but there’s a lot of camaraderie in our fanbase which creates a really safe and accepting space,” she says.

When I met my first girlfriend I felt so free. I just felt so invincible and so unstoppable

Lynn Gunn

Acceptance is something the band are advocating for even more vocally since Donald Trump took office. “It’s a big push and pull between people who are really siding with him and people who are completely against him,” she says. “But [LGBTQ rights] is one of those things that, if he wasn’t in office, might not have surfaced. People might not have been like: ‘Oh, we need to fix this and really get on top of it.’” They’ll be donating a portion of proceeds from their autumn tour to the Ally Coalition, a venture created by the band Fun to encourage people in the entertainment industry to support equality. “I think Trump has inspired a lot of people to be really vocal with each other,” she adds. “A lot more people are on the right side of history, rather than his side.”

Lynn came out to her parents as a teenager, and describes writing her mother a letter before setting off on her very first tour. “I’d just graduated high school and the following summer I met my first girlfriend, and I felt so free, I’d never felt the feeling of being in love before, I just felt so invincible and so unstoppable,” she smiles. “I felt like a huge weight had been taken off [after writing the letter], but I also felt so terrified because I didn’t know how they’d react. It was a little rocky at first but I think that was mostly my parents’ concerns as to how our family outside our immediate family would react. But everyone’s been super-supportive. I really lucked out with that.”

Something else she lucked out with is that Alex and Brian – who join us later in the coffee shop – are close friends. I ask if they worry their beginnings in a tight-knit alternative scene will lead to them being pigeonholed for ever as a “Kerrang! band”. “I think it’s in our power to control that,” Gunn says. “I feel like we exist anywhere. I think, very recently, more people are picking that up. We came from that scene, but we’re growing beyond that.” That growth, it seems, is personal as well as musical.